1. Field of the Invention
The present invention relates to parallel shaft reduction gears used in, for example, cooling tower fan drives, and particularly to a parallel shaft reduction gear equipped with a backstop mechanism for preventing reverse rotation of the output shaft thereof.
2. Description of the Related Art
There are parallel shaft reduction gears each used together with a motor and equipped with a backstop mechanism such as a one-way clutch for preventing reverse rotation of the output shaft thereof.
FIG. 4 is a fragmentary enlarged view illustrating a sprag type one-way clutch as an example of the backstop mechanism.
This one-way clutch 100 is a publicly-known mechanism, having cams 106 in between an inner ring 102 and an outer ring 104. If the outer ring 104 is secured to a casing (not shown), the rotation of the inner ring 102 is limited to one direction (direction R in the figure), and the cams 106 prevent the reverse rotation of the inner ring 102.
If such a backstop mechanism capable of limiting the direction of rotation is installed in one of the rotary shafts constituting the reduction gear, the reverse rotation of the output shaft is prevented and only rotation of the normal direction is transmitted to the target object to be driven.
Conventional parallel shaft reduction gears equipped with such a backstop mechanism are, however, not designed to provide easy maintenance for the backstop mechanism. For replacing/repairing the backstop mechanism, the motor and other peripheral hardware must be all removed, and changeover and maintenance are not easy to perform.